A number of known tuning systems, such as those disclosed in German Offenlegungsschrift [Laid-open Application] No. 2,703,861 and German Offenlegungsschrift No. 2,720,170, corresponding to allowed U.S. Pat. No. 4,195,314, include a counter whose counter state determines the frequency to which the receiver is tuned, or the tuned frequency, and can be varied up or down by means of counting pulses. The content of the counter stages thus controls the tuning process.
Such a tuning circuit has the characteristic that the frequency to which it is tuned changes in small steps since each counting pulse advances the counter by one counting step. A timing member in the tuning circuit can be used to limit the rate of change of the tuned frequency, thus preventing the step-wise setting of the tuning system from being undesirably felt, for example, in the low frequency portion of the receiver. The timing member also prevents overshooting of the circuit beyond a tuned frequency given by a certain counter state. The timing member gives the tuning circuit a certain inertia, which is necessary, however, to avoid the above-mentioned drawbacks. The result of this inertia is that the tuning circuit is unable to follow rapid changes of the counter state in every case. However, particularly in connection with radio receivers, there exists the requirement of being able to quickly change the tuned frequency between two widely diverging values within a set tuning band.